This invention relates to sleeving for the protection of elongated substrates and especially to convolute sleeving having improved flexibility and radial stiffness.
Convolute sleeving is used across a broad range of industrial applications, particularly in electronics, aerospace and automotive applications to provide protection to elongated substrates, such as wiring harnesses and fluid conduits, particularly hydraulic lines and fuel lines, from harsh environments. A wiring harness, fuel line or hydraulic line may be subjected to extremes of heat and cold, radio frequency/electromagnetic interference (RFI/EMI), severe vibration, abrasion and physical impact damage when used in the engine compartment of an aircraft or automobile or on an orbiting satellite.
Convolute sleeving is often used to ensheath and protect such elongated substrates from heat, cold, abrasion, vibration and impact damage as well as to provide acoustical damping or shield electrical conductors from RFI/EMI. Because such sleeving is formed having a series of alternating crests and troughs, it has both excellent radial stiffness and bending flexibility. The radial stiffness prevents the sleeving from kinking and collapsing when bent and the flexibility allows it to follow almost any curved shape and, thus, conform readily to the path of the elongated substrate without adding any significant bending stiffness which would otherwise make the substrate difficult to install.
Convolute sleeving is generally more expensive to produce than non-convolute sleeving because extra processing steps are required to produce the convolutes. For example, convolute sleeving formed from an extruded plastic tube requires an additional machine having circulating mold halves which engage the tube and form the convolutes along the tube while it is being drawn from the die in a semi-molten state. There is clearly a need for a convolute sleeve which is more easily and economically manufactured.
The invention concerns an elongated convolute sleeve for protecting elongated substrates. In one embodiment, the sleeve comprises a plurality of tubular first segments positioned coaxially in spaced relation lengthwise along an axis. Each of the first segments is comprised of a plurality of flexible, resilient first filamentary members knitted in a plurality of first courses. Each of the segments has outwardly flared ends oppositely disposed. The sleeve also comprises a plurality of tubular second segments, each being formed of a plurality of second filamentary members having relatively greater flexibility than the first filamentary members. The second filamentary members are knitted in a plurality of second courses, each of the second segments being coaxially positioned along the same axis as the first segments and joined with the first segments end to end in an alternating pattern by interknitting the ends of the second segments with the flared ends of the first segments. The first segments form a plurality of troughs and the second segments form a plurality of crests projecting radially outwardly from the sleeve.
Another embodiment of the convolute sleeve according to the invention comprises a tubular body having a nominal diameter and formed of a plurality of flexible, resilient filamentary members knitted in a plurality of circumferential courses extending substantially coaxial with and lengthwise along an axis. A plurality of resilient hoops, preferably formed from a monofilament, are positioned in spaced relation lengthwise along the tubular body coaxially with the axis. The hoops each have a respective diameter greater than the nominal diameter of the body and are interlaced with the filamentary members, preferably by laying in, and thereby fixing the hoops to the body. The diameter of the body is substantially equal to the hoop diameters at spaced intervals along the body where the hoops are interlaced with the filamentary members because the monofilament forming the hoops is relatively stiffer than the filamentary members forming the tubular body. The hoops force the body outwardly to form crests in spaced relation to one another along the axis, troughs being formed by the body between each hoop.
Yet another embodiment of the convolute sleeve according to the invention comprises a tubular body having a plurality of first and second longitudinally extending regions arranged in spaced relation coaxially along an axis. The first and second regions are positioned adjacent one another in an alternating pattern and are formed from a plurality of filamentary members knitted in a plurality of courses. Each course comprises a plurality of loops extending circumferentially around the axis. To form the crests and troughs of the convolute sleeve, the stiffness of the first regions are different from the stiffness of the second regions. The stiffness of the regions maybe varied by changing the material from which the regions are knitted or by varying knitting parameters such as the density or length of the loops forming the courses.
It is an object of the invention to provide an elongated protective sleeve.
It is another object of the invention to provide a protective sleeve which is manufactured by knitting.
It is still another object of the invention to provide a convoluted knitted sleeve.
It is again another object of the invention to provide a convoluted sleeve wherein the convolutions are formed by interknitting filamentary members having different stiffness.
It is still another object of the invention to provide a convoluted sleeve wherein the convolutions are formed by varying the knitting parameters as a function of length along the sleeve.
It is yet another object of the invention to provide a convoluted sleeve wherein the convolutions are formed by a plurality of interlaced circular hoops.
These and other objects and advantages of the invention will become apparent upon consideration of the drawings and the description of the preferred embodiments.